The present invention relates to a flame-passage device for non-annular gas turbine combustion chambers.
The constant quest for increases in the performance levels of gas turbines, and in the intervals between the various stoppages for maintenance, as well as the pressing need to reduce pollutant emissions as far as possible, makes necessary optimisation of all the components which are inserted in the so-called hot gas path.
In particular, the combustion system, which acts as an energiser for the thermal-carrier fluid, is the true heart of the turbine engine, and therefore defines its level of emission, and, according to the service life of its own components, the intervals of functioning between machine stoppages, in order to carry out inspections of the combustion chambers.
The requirement to develop the machines in operation, with increases in the compression ratios and fire temperatures, are a further reason for emphasising the criticality of the hot components.
Reduction of the emissions, with an increase in the service life of the components, and optionally also in the efficiency of the system, also constitutes a general target which undoubtedly has an impact on the clientele of heavy duty machines, and is a stimulating technological challenge for the designers.
In particular, in the case of machines which have had a certain length of service, it is possible to gather sufficient statistical data to determine the parameters and details which are critical in achieving overall improvements, such as to justify the cost of the design and subsequent marketing, optionally in uprate packages for the aftermarket.
A major technical problem therefore consists substantially of determining solutions which permit achievement of maximum satisfaction of the client for the three aforementioned aspects, all by means of innovative creations which are economically acceptable.
In order better to understand the technical problems which are involved in the present invention, at this point reference is made to the following state of the art.
The solutions which are currently used in order to achieve the three above-described objectives (greater efficiency, longer service life of the machine, and fewer pollutant emissions), are not in general combined in a single product, but are on the other hand implemented in ranges of alternative components.
In order to increase the service life, and thus the intervals of inspection of the combustion chambers, use is made of materials, such as stellite 6, deposited onto elements which may become worn by relative vibratory motion, super-alloys with a nickel/cobalt base, with high levels of mechanical characteristics and of resistance to corrosion at high temperatures, additions of a ceramic type, to reduce the temperatures of the metal (for the same cooling flows), and optimisation of the design of the components, on the basis of experience acquired.
A previous solution, consisting of six combustion chambers arranged in two rows of three parallel combustion chambers stacked on both sides of the machine, in an arrangement at right-angles to the machine axis, by means of interposition of 90xc2x0 connection elbows between the liners and transition pieces, was then replaced by an arrangement characterised by chambers inclined by only a few degrees in relation to the machine axis, and insertion of the liners directly in the transition piece, and therefore without the need for further connection elements.
Particular problems of the known art also become apparent by taking into consideration the operations of fitting and removal of the various components.
In the conventional case, the procedure followed consists of opening the covers of the chambers including burners, removing one of the liners of the chambers which are connected to the adjacent chambers by means of a single flame-passage tube, then removing the entire flame-passage unit from the flanged pipe which connects the two cases of the said chambers, such that the case of the said chambers has its liner removed, and the subsequent chamber is also connected at this point only by the flame-passage tube, for connection to the successive chamber.
The procedure continues iteratively, with removal of all the liners and the corresponding crossfires.
Since at this point the crossfires have been removed, the flanged pipes outside the latter are free to be disconnected, thus permitting removal also of the individual cases.
However, the complexity and intricacy of this succession of removal operations should be noted.
In particular, the arrangement of the combustion chambers in the gap between the flanging on the turbine case, and the pipe to supply induction air to the compressor (which is further limited in the lower area by the presence of the front support fork of the machine), makes it impossible to fit and remove the combustion chambers according to the method currently used for all the multi-canned applications.
The object of the present invention is thus to provide a flame-passage device for non-annular gas turbine combustion chambers, comprising a combustion system which is innovative both from the point of view of the overall arrangement, and from that of its component elements.
A further object of the invention is to provide a flame-passage device for non-annular gas turbine combustion chambers, which is designed particularly for the aftermarket, and is therefore easy to fit and remove.
Another object of the invention is to provide a flame-passage device for non-annular gas turbine combustion chambers, which has a high level of efficiency and mechanical reliability.
These and other objects are achieved by a flame-passage device for non-annular gas turbine combustion chambers, of the type comprising a tubular body, which is provided with a plurality of cooling holes, for cooling of the swirl-cooling type, wherein the said tubular body is inserted in a flanged pipe, which connects the cases of two successive combustion chambers, characterised in that it has a first end with a cylindrical shape, and a second end with an oval shape, wherein the second, oval end is provided with three rings, for anchorage of the corresponding combustion chamber to the case.
According to a preferred embodiment of the present invention, a cylindrical collar can be fitted at the said first, cylindrical end of the said tubular body, and an oval collar can be fitted at the said second, oval end of the said tubular body.
According to another preferred embodiment of the present invention, the cases which belong to each combustion chamber each have a circular hole, for connection to the cylindrical end of the said flame-passage, tube, which takes place by means of interposition of the said cylindrical collar, and the cases of each combustion chamber each have an oval hole, for connection to the oval end of the said flame-passage tube, which takes place by means of interposition of the said oval collar.
According to another preferred embodiment of the present invention, the three rings, which are present at the said second, oval end, permit anchorage of the corresponding combustion chamber to the case, by means of use of a corresponding fork.
According to a further preferred embodiment of the present invention, on the ends of the said flame-passage tube, an anti-wear deposit made of stellite 6 or another hard material is provided, in order to cover the contact surface in the interface with the said collars of the liners.
In addition, the flame-passage tube can be translated along almost the entire length inside a liner body, thus releasing immediately the connection flanging between the various cases of the combustion chambers.
Further characteristics of the invention are defined in the claims attached to the present patent application.